1. Technical Field
The present invention relates to a method for finding the distance from the edge of a wafer to the location where photoresist was removed around the circumference of the wafer via an edge bead removal process.
2. Background Information
Over the past several decades, the semiconductor has exponentially grown in use and popularity. The semiconductor has in effect revolutionized society by introducing computers, electronic advances, and generally revolutionizing many previously difficult, expensive and/or time consuming mechanical processes into simplistic and quick electronic processes. This boom in semiconductors has been fueled by an insatiable desire by business and individuals for computers and electronics. Therefore, there is a need for faster, more advanced computers and electronics. To satisfy this need, quality and efficiency is required, whether it be on an assembly line, on test equipment in a lab, on the personal computer at one's desk, or in home electronics and toys.
Manufacturers of semiconductors have made vast improvements in end product quality, speed and performance as well as in manufacturing process quality, speed and performance. However, there continues to be demand for faster, more reliable and higher performing semiconductors. To assist these demands, better inspection is necessary to increase yields. One area that has been generally ignored is the edge of the semiconductor wafer. It is believed that inspection of such edge area will lead to better information on defects, thereby enabling improved process control and improved wafer yields.
Typically, during conventional applications of masking layers or photoresist layers onto a semiconductor wafer, a desired amount of liquid photoresist is applied to the top surface of the semiconductor wafer while the wafer is being rotated. Thus, as a semiconductor is rotated, the photoresist materially spreads radially outward from the center of the semiconductor wafer and toward the edge of the semiconductor wafer such that the entire top of the wafer is coated with a layer of photoresist. Excess amounts of photoresist can accumulate and form a mound or bead of photoresist on the outer edge of the semiconductor wafer. In order to illuminate the “edge bead” of photoresist, a coating system known as an edge bead removal (EBR) unit can be employed.
Two types of EBR units are well known in the art, chemical and optical. Chemical EBR units include a nozzle, which dispenses a solvent referred to as EBR fluid, onto the photoresist of the semiconductor wafer. The solvent dissolves or develops away the photoresist and allows for easy removal of the photoresist from the edge of the semiconductor wafer. In an optical EBR unit, the photoresist at or near the edge of the semiconductor wafer is exposed to light. During subsequent development processes, the exposed photoresist is removed. Photoresist, which remains on the semiconductor wafer, forms a mask for subsequent processing operation.
Typically, several different EBR units are utilized during fabrication of integrated circuit devices on semiconductor wafers. The use of different EBR units commonly results in a random or non-uniform stacking of substrate layers at or near the edge of semiconductor wafer. The random or uneven stacked substrate layers can lift and detrimentally re-deposit onto the semiconductor wafer. The re-deposited substrate material can contaminate the semiconductor wafer and cause defects in the integrated circuit devices formed on the wafer.
In many applications, inspection of the edge area of a semiconductor wafer corresponds directly to obtaining information on defects within the semiconductor wafer including delamination of thin films, chipping and cracking of the wafer, resist removal metrology, and particle detection. Therefore, it is desirous to find the distance from the edge of the wafer to the location where the photoresist was removed as a tool in the semiconductor wafer inspection process.